1. Field of Invention
The invention relates to pressure indicating methods and apparatus in general, and more particularly to tire pressure indicators and easy access tire fill valves for single and dual wheel tire assemblies and methods for monitoring vehicle tire pressure. Other aspects of the invention relate to a wheel clip assembly that secures a wheel cover to a wheel rim. Aspects of the invention also relate to an aerodynamic wheel cover that reduces drag and lowers the operating temperature of the wheel.
2. Description of the Related Art
Fuel and tires represent the greatest operating cost for a single tractor/trailer or an entire fleet. If a truck tire that normally operates at one hundred pounds per square inch is twenty-five to thirty percent underinflated, which causes excessive tread wear due to heat and friction and reduces fuel efficiency due to resistance and drag. At today's average cost of two hundred to three hundred dollars per tire, under inflation could account for as much as seventy-five dollars per tire in tire costs alone. Under inflation also negatively impacts the longevity of tire casings. Proper air pressure maintenance assures that tires can be recapped up to five times.
Prior art methods and devices for maintaining proper tire pressure include mechanical spring powered hand pressure gauges carried by the driver and used to periodically check tire pressure and to fill tires to proper levels. Tire gauges or indicators, which are permanently mounted to the tire fill-valve, provide a readout of the tire pressure when viewed by the truck operator.
Truck drivers most commonly use the manual pressure gauges to check tire inflation pressure, usually after first tapping the tire with their foot or a tool and finding that pressure is low. Such a check detects a low tire only after a significant loss of tire pressure. With a slow leak, a tire may have been operating at low pressure for some time and some tire degradation may already have occurred. Also, over pressure is not detectable by such tapping.
Low tire pressure increases the amount of tire tread contacting the highway. This can develop into a condition referred to as “over steer”. This condition occurs when the low tire, if on the rear of a car, actually steers the car due to the increased tire footprint on the rear when the car is affected by side winds or is on a steeply crowned road surface. In such cases, the driver may lose directional control of the vehicle.
Excellent examples of the consequences of under inflation of tires are found along the shoulders of interstate highways, where black tire treads have separated from the tires due to low tire pressure of the inner tire on the dual wheels. Such tires have generated so much road friction, resulting in heat in the tire, that the tire tread comes off of the tire casing. Truck companies cannot afford to have employees check the eighteen tires on every trip and therefore truck drivers may check tires only once or twice a year on over-the-road trucks, which may be driven up to 125,000 miles per year.
Environmental and danger hazards of such tire treads and such practices are obvious. Hazardous material truckers are suppose to check the tires every one hundred miles driven or every two hours of driving. This very infrequently occurs.
Permanently mounted tire pressure gauges and pressure indicators may be on a tire valve stem adjacent the rim are small in size and require the operator to bend down to the tire before the operator can see the gauge pressure. Some gauges mounted away from the rim tire valve are actually covered with a cover and require an effort on the part of the operator to remove the cover before checking the gauge(s). No known permanently mounted tire pressure indication systems offer an easily seen gauge which can be easily viewed by the truck operator as the operator inspects the wheels of a stationary vehicle to see if inflation pressure is in the proper range.
One known specific example of a permanently mounted tire inflation indicator is found in U.S. Pat. No. 3,958,526. An under-inflation type warning system is disclosed. A collapsible bladder mounted axially on the wheel is connected to a tire and is inflated whenever tire pressure falls below a predetermined level. However, there is no warning provided by this system for a slowly leaking tire or for over-inflation. There is no easily visible gauge which shows pressure in the tire at all times and guides the operator in inflating the tire to the proper level. The system uses conventional rim-attached tire fill-valves.
Another example may be found in U.S. Pat. No. 4,387,931, where a pressurized container regulated to desired tire pressure is continuously connected to all of the tires to thus maintain them all at the proper pressure level. However, this system provides no actual gauge reading(s) of tire pressure, and a failure of the pressure regulator or the container could result in an undetected over-pressurized or under-pressurized condition in all of the tires.
A dual-tire, wheel assembly tire pressure indicating system is disclosed in U.S. Pat. No. 4,953,395. The gauge or gauges are located in the center hub of the wheel and are covered with a removable cover, requiring the operator to bend down to wheel level to uncover and view the gauges. Further, there is no indication that the gauges offer any area markings thereon to indicate proper or improper inflation, nor is these any analog pressure readout to aid in inflating the tire to the optimal pressure of one hundred pounds per square inch, nor is there any identification of which gauge is for the front and which is for the rear tire of a dual wheel assembly.
Another conventional dual-tire, wheel assembly tire pressure indicating system is disclosed in U.S. Pat. No. 5,770,797. The '797 tire pressure indicating system includes a pair of readout pressure gauges mounted on a full wheel streamlined hubcap. The hubcap is mounted to the outside wheel of a dual wheel assembly using a U-shaped bracket connected to the wheel through the wheel bolts with the hubcap connected thereto by quarter turn fastener assemblies.
There is a problem associated with such prior art devices in that if the device becomes detached from the tire fill-valve while the vehicle is in motion, the device may become a high velocity projectile and thus present a safety hazard. Another problem with such prior devices is that, because of the eccentricity of the load they add to the tire, the tire may become unbalanced, thus presenting a safety problem and causing an uneven and unsafe ride.
Another problem of such prior art devices is that they require use of a mounting device for the tire pressure gauges, such as a hubcap assembly mountable to the front wheel of a deep dish dual wheel assembly through a bracket assembly connected by wheel bolts or nuts to oppositely located studs of the outside wheel of a dual wheel assembly. Such a tire pressure indication system is disclosed in U.S. Pat. No. 5,770,797 herein incorporated by reference. This unnecessary practice of providing a tire pressure indication system mounted to a hubcap assembly increases the cost and weight associated with the tire pressure indication system.
Typical tire/wheel arrangements for heavy-duty roadway vehicles, such as tractors, trailers, and trucks, have to contend with situations relating to the optimal performance of the vehicle. A nut and bolt assembly, which typically extends from the wheel rim, may cause drag and effect optimal performance of the vehicle. Even further, during the travel or braking of the vehicle, the tire/wheel arrangement may experience a high operating temperature. The high operating temperature may have an undesirable effect on vehicle performance and/or result in pressure losses in the tire. Even further, in certain trucking applications, such as hauling of hazardous materials, the Department of Transportation (DOT) requires certain safety standards in monitoring tire pressure. The DOT requires that trucks stop every two hours or every one hundred miles in order to check air pressure in every tire. Because such trucks are frequently stopped so the tires may be checked for pressure losses, a vehicle operator periodically may have to pressurize the tires. There is a need for a new tire/wheel arrangement that permits and maintains optimal performance of the vehicle by reducing drag and lowering the operating temperature of the tire/wheel arrangement.